It has been shown that some of the lysine residues in the outer membrane proteins from Escherichia coli have been modified to aldehydes. This research is to evaluate the kinds and extent of aldehydic cross-linking in the outer membrane. Experiments will be performed to assess the significance of these cross-links on organization, stability, assembly, and permeability of the outer membrane. The experimental approach is to chemically stabilize these aldimine cross-links to that they may be identified and separated by amino acid analysis, purified by chromatography, and completely identified by mass spectrometry.